Italian patent IT 1199046 shows a valve of the above-cited type, exhibiting a sleeve made of non-magnetic material which contains both the fixed group and the mobile group (both made of magnetic ferrous material). The non-magnetic sleeve, which is surrounded by an electromagnetic coil, is screwed at one end to the valve body and at its other end bears a locking ring nut. The normally-adopted solution, for avoiding the presence of a thread on the non-magnetic sleeve, is to weld at least one end of the sleeve to at least one element made of ferrous magnetic material.
Even this solution, however, does not eliminate drawbacks, among which the cost and time needed to do the actual welding and the resulting structural weakening in the welded zone.
U.S. Pat. No. 2,968,464 discloses an electromagnetically-actuated two-way valve as in the preamble of claim 1.
The main aim of the present invention is to provide a valve, constructionally simple and economical, which is able to obviate the above-mentioned drawbacks in the prior art.
An advantage of the valve is that it does not require the use of any elements made of non-magnetic materials.
A further advantage is that the invention makes available a valve lacking in welded zones and having a high mechanical resistance, especially to fatigue.
A further advantage of the invention is that the electromagnetic coil for actuating the valve can work with both direct and alternating current, without any modifications to the valve. In particular the coil can function in alternating current with no use of additional elements, such as for example brass washers and the like applied to the fixed group, as generally occurs in known valves.
A further advantage with respect to known valves is the reduction in the time necessary for opening and closing the valve itself.
These aims and advantages and more besides are all attained by the present invention, as it is characterised in the appended claims.